1. Field of the Invention
The present invention relates to a semiconductor device manufacturing apparatus for manufacturing semiconductor devices on semiconductor substrates and more particularly, it relates to an improvement of a semiconductor device manufacturing apparatus including a vertical type of heating furnace for forming films on semiconductor substrates.
2. Description of the Prior Art
In the past, various semiconductor device manufacturing apparatus have been known for forming films, such as oxide films, nitride films, polysilicon films, on silicon substrates or the like for forming a semiconductor device. As such semiconductor device manufacturing apparatus, various oxidizing equipment and CVD (Chemical Vapor Deposition) equipment have been used.
Such semiconductor device manufacturing apparatus comprise a horizontal heating furnace, and others comprise a vertical heating furnace. The structure of a horizontal heating furnace is disclosed in, for example, an article by L.E. Katz et al. entitled "High Pressure Oxidation of Silicon by the Pyrogenic or Pumped Water Technique", Solid State Technology, Dec. 1981, pp 87-93. In forming films, a plurality of semiconductor substrates are disposed approximately vertically in a horizontal heating furnace, whereas semiconductor substrates are juxtaposed horizontally with predetermined spacings in a vertical heating furnace.
FIG. 1 is a diagram showing a holder used for holding silicon wafers in a conventional vertical heating furnace. As a material of this holder, for example, quartz, silicon carbide, or polysilicon is used. In FIG. 1, each of three supports 8 of a holder 7 is formed with grooves 9 for inserting silicon wafers 1 in a longitudinal direction of each of the supports 8, with a predetermined spacing between grooves. The silicon wafers 1 are inserted into the grooves 9 one by one and then are placed within a vertical heating furnace of a semiconductor device manufacturing apparatus to be heated. Then, raw material gas for forming films on the silicon wafers 1 is introduced into this vertical heating furnace.
In a conventional semiconductor device manufacturing apparatus, a holder of silicon wafers is constructed as described above. If silicon wafers are inserted into grooves of the holder, a part of the silicon wafers inserted into the grooves becomes covered by a part of the support. This causes a problem in which the films formed do not grow uniformly, because raw material gas for forming films do not sufficiently reach this portion, and a difference in film thickness occurs on the surface of silicon wafers.
There also has been a problem in which this portion is contaminated by bringing a part of silicon wafers into contact with the edge of grooves by mistake in inserting silicon wafers into grooves.